U.S. Pat. No. 2,845,335 discloses a four-step process for converting a hydrocarbon stream to a mixture comprising unsaturated hydrocarbon. The reactor system comprises four similar regenerative reactors, with reactors one and two comprising a first parallel reactor pair which are separated from a second parallel reactor pair (reactors three and four) by at least one mixing region. The reactor system is preheated before the first step of the process.
In one embodiment, the reference discloses a first step involving flowing a hydrocarbon through the first reactor pair toward the second reactor pair, with a first portion of the hydrocarbon flowing through reactor one and a second portion flowing through reactor two. Pyrolysis products flow away from the mixing region, through the second reactor pair, a portion of the pyrolysis products being deposited as coke in reactors one-four. In a second step, fuel and air are conducted toward the mixing region, the fuel being conducted through reactor three and the air being conducted through reactor four. The fuel and air combust in the mixing region, with the combustion products flowing away from the mixing region through the first reactor pair (a portion of the combustion products flowing through each of reactors one and two), thereby (i) heating the reactor system for step 3 and (ii) oxidizing coke deposited in reactors one, two, and four. The third step is similar to the first step, with pyrolysis products flowing away from the mixing region, through the second reactor pair and again depositing coke in reactors one-four. In a fourth step, fuel and air are again conducted toward the mixing region, but now the fuel is conducted through reactor four and the air is conducted through reactor three (the reverse of step two). The fuel and air combust in the mixing region, with the combustion products flowing away from the mixing region through the first reactor pair, thereby (i) heating the reactor system for step one and (ii) oxidizing coke deposited in reactors one, two, and three.
It is desired to increase the efficiency of the process.